The present invention relates to an electronic musical instrument, and more particularly relates to improvements in control of musical tone generation in response to controller operation on an electronic organ, an electronic piano or a portable electronic musical instrument, and the like.
In this specification, the term "a controller" refers to not only a white or black key but also a push botton key, a foot plate of an expression pedal mechanism, a knee lever, a joy stick operator on an electronic musical instrument. Further the term "musical tone control parameter" refers to all sorts of musical tone control parameters such as tone volume, tone colour, tonal pitch, tempo, depth and speed of vibrato and tremolo, etc.
Control of tone generation in an electronic musical instrument such an electronic organ is basically carried out by manual key operation which controls the state of an associated key switch. This mode of control, however, is too simple in tone generation characteristics to correctly reflect delicate changes in a player's feelings.
In an attempt to make up for this demerit in tone generation characteristics, it was already proposed to provide an electronic musical instrument with a so-called touch-response function which varies tone generation characteristics on the basis of the magnitude of key operation for richer reflection fo player's feelings. In accordance with this touch-response funcetion, the tone volume, the tonal pitch and the tone colour of a musical tone are controller in accordance with player's finger motion during the rise and decay periods of the musical tone.
In the case of a touch-response type control system proposed in U.S. Pat. No. 3,705,254, a relative displacement between a magnet and a coil is caused by key operation to generate a induced electromotive force output which is used to control the response to key touch. In this case, signal processing in analog mode requires a complicated hardware construction and, consequently, increased production cost. In addition, no stability in operation can be much expected.
Another touch-response type control system is disclosed in U.S. Pat. No. 4,079,651 in which an electrically conductive and elastic piece is deformed in response to key operation and such deformation establishes sequential short circuits between fixed contacts arranged on a substrate to change the resistance stepwise. Such change in resistance is converted into voltage output which is used to control the response to key touch. Also in this case singal processing is carried out in analog mode, which requires a complicated hardware construction and high production cost. In addition, it is rather infeasible to leave a too small pitch between adjacent fixed contacts from the view points of contact formation and circuit wiring. For these reasons, no subtle control of touch-response can be expected in the case of this prior proposal.
A further touch-response type control system is proposed in Japanese Patent Application Laid-Open Sho. 58-18812 in which a disc type mobile contact is driven for rotation by key operation. Following the rotation, the mobile contact is brought into sequential contact with a plurality of fixed contacts arranged on the substrate to generate digital signal outputs which are used for control of tone generation. This type of control system is well suite for an electronic musical instrument which generates musical tones by means of digital signal processing by a mirco computer recently in fashion. In this case also, subtleness in signal generation is much degraded by difficulty in contact arrangement. In addition, the number of output lines is directly affected by that of the contacts used in the system, thereby commplicating the construction and increasing the production cost.